Positive electrode precursor material and preparation method thereof, positive electrode material and lithium ion battery

Abstract

The invention provides a positive electrode precursor material and a preparation method thereof, a positive electrode material and a lithium ion battery. The positive electrode precursor material sequentially comprises a precursor inner core, a first coating layer, a second coating layer and a third coating layer from inside to outside, the precursor inner core comprises a nickel-cobalt-manganese hydroxide precursor material, and a lanthanum element and a boron element doped in the nickel-cobalt-manganese hydroxide precursor material; the first coating layer comprises a nickel-cobalt-manganese oxide, the second coating layer comprises a mixed material of the nickel-cobalt-manganese oxide and a high-entropy oxide, and the third coating layer comprises the high-entropy oxide. According to the invention, lanthanum and boron in the precursor inner core are doped, so that the purpose of improving the stability of the body structure is achieved; the multi-stage coating layer is cooperatively matched, so that lattice defects can be repaired, and meanwhile, interface side reaction can be inhibited; and the stress of the large-particle positive electrode material in the circulating process can be relieved, and interface fracture is avoided, so that the capacity, the rate and the circulating performance of the positive electrode material are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and relates to a positive electrode precursor material, a preparation method thereof, a positive electrode material and a lithium ion battery. BACKGROUND

[0002] Fossil fuels are consumed in large quantities, and humans are facing unprecedented energy crises and environmental pollution problems. Lithium ion batteries are widely used in all aspects of human life due to their high energy density, long cycle life, green environmental protection and other advantages. However, the specific capacity of the positive electrode material of the lithium ion battery is low, and the performance decays quickly, which seriously restricts the development of the lithium ion battery. Compared with other positive electrode materials, the ternary positive electrode material has higher capacity and better cycle performance, and has moderate price, and is an important material for realizing high energy density of the lithium ion battery.

[0003] In the current field of positive electrode materials of lithium ion batteries, large-particle-size ternary materials (NCM, LiNi x Co y Mn z O2, x≥0.9) are highly concerned due to their high tap density, low specific surface area and excellent volume energy density. However, in the process of charging and discharging, the traditional large-particle-size material has anisotropic volume change (especially in the high-nickel system), and when the particle size D50 of the ternary precursor is greater than 8 μm, the tap density is increased (≥2.4 g / cm3) to increase the volume energy density. However, the anisotropic volume change in the process of charging and discharging causes stress accumulation in the particle, resulting in crack propagation and interface side reactions, which significantly reduces the rate performance and capacity retention. Lithium-nickel mixing and H2-H3 phase change cause microcracks to extend along the grain boundary, and electrolyte invasion accelerates the generation of rock salt phase, finally resulting in particle pulverization and a large decrease in capacity.

[0004] In addition, in order to improve the performance of the material, a single doping or coating method is often used in the prior art, for example, Mg, Al, Ti and other elements are introduced for doping, which can effectively inhibit the structural degradation of the material in the cycle process; and the surface is coated with carbon, aluminum oxide and other substances, which can improve the conductivity of the material and reduce the side reaction. However, the above modification methods still cannot solve the following problems: for example, the mismatch of the thermal expansion coefficient between the coating layer and the substrate causes interface peeling in the cycle, resulting in weak interface bonding; and for example, a too thick coating layer (>30 nm) hinders the diffusion of Li+, resulting in blocked ion transmission and reduced rate performance.

[0005] Therefore, how to slow down the stress in the cycle process and improve the structural stability of the ternary positive electrode material while ensuring that the ternary positive electrode material has excellent properties such as high tap density, low specific surface area and excellent volume energy density is a technical problem that needs to be solved. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a positive electrode precursor material and a preparation method thereof, a positive electrode material and a lithium ion battery. The present application can lock the oxygen stable lattice through the lanthanum and boron doping in the core of the precursor, so as to achieve the purpose of improving the stability of the bulk structure; the multi-level coating layer can repair the lattice defects, and can also inhibit the interface side reaction; and can also slow down the stress of the large particle positive electrode material in the cycle process, so as to avoid the interface fracture, thereby improving the capacity, rate and cycle performance of the positive electrode material.

[0007] In order to achieve the purpose of the present application, the following technical solutions are adopted:

[0008] In a first aspect, the present application provides a positive electrode precursor material, which comprises a precursor core, a first coating layer, a second coating layer and a third coating layer from inside to outside.

[0009] The precursor core comprises a nickel-cobalt-manganese hydroxide precursor material and lanthanum and boron doped in the nickel-cobalt-manganese hydroxide precursor material.

[0010] The first coating layer comprises a nickel-cobalt-manganese oxide, the second coating layer comprises a mixed material of a nickel-cobalt-manganese oxide and a high-entropy oxide, and the third coating layer comprises a high-entropy oxide.

[0011] The definition of the high-entropy oxide is an oxide with five or more metal elements.

[0012] The positive electrode precursor material of the present application has high tap density, low specific surface area and excellent volume energy density, adopts a unique core-shell structure design, the precursor material core doped with lanthanum and boron, boron occupies Li site to inhibit phase change, lanthanum strengthens the stability of the oxygen framework, improves the stability of the bulk structure, can slow down the stress of the large particle positive electrode material in the cycle process, and avoid interface fracture; and then cooperates with the multi-level coating layer structure, the first coating layer containing nickel-cobalt-manganese oxide can have good lattice matching and binding effect with the precursor core, the second coating layer of the mixed material of the nickel-cobalt-manganese oxide and the high-entropy oxide realizes smooth transition of the mechanical and chemical properties from the precursor core to the high-entropy oxide layer, and transitions to the third coating layer with only high-entropy oxide, improves the chemical and electrochemical inert protection, and utilizes the characteristics of the high-entropy oxide, so that the high-entropy elements diffuse from the inside to the surface, repair the lattice defects, and inhibit the occurrence of interface side reaction, and also improve the thermal stability of the material, inhibit H2-H3 phase change; at the same time, the coating layer structure can also relieve the mechanical stress caused by the volume change and phase change in the core, prevent structural damage and performance degradation; and improve the capacity, rate and cycle performance of the positive electrode material.

[0013] The doping of lanthanum and boron in the core of the application and the design of the multi-stage coating layer must be synergistic at the same time, and from the first to the third coating layer stage, the transition stage with the first coating layer and the second coating layer, to realize the revolutionary breakthrough and synergistic improvement of structural stability, fast charging ability, thermal safety and industrialization economy under high voltage.

[0014] The following is a preferred technical solution of the application, but not as a limitation on the technical solutions provided by the application. Through the following preferred technical solutions, the technical purposes and beneficial effects of the application can be better achieved and realized.

[0015] Preferably, the precursor core includes a core and a nuclear layer coated on the surface of the core, and the first coating layer is coated on the surface of the nuclear layer.

[0016] Preferably, the core includes a nickel-cobalt-manganese hydroxide precursor material and lanthanum and boron elements doped in the nickel-cobalt-manganese hydroxide precursor material.

[0017] Preferably, the doping amount of lanthanum in the core is 0.05at%~0.15at%, such as 0.05at%, 0.06at%, 0.07at%, 0.08at%, 0.09at%, 0.1at%, 0.11at%, 0.12at%, 0.13at%, 0.14at% or 0.15at% and the like.

[0018] Preferably, the doping amount of boron in the core is 0.01at%~0.1at%, such as 0.01at%, 0.02at%, 0.03at%, 0.04at%, 0.05at%, 0.06at%, 0.07at%, 0.08at%, 0.09at% or 0.1at% and the like.

[0019] Preferably, the nuclear layer includes a nickel-cobalt-manganese hydroxide precursor material and boron elements doped in the nickel-cobalt-manganese hydroxide precursor material.

[0020] Preferably, the doping amount of boron in the nuclear layer is 0.01at%~0.1at%, such as 0.01at%, 0.02at%, 0.03at%, 0.04at%, 0.05at%, 0.06at%, 0.07at%, 0.08at%, 0.09at% or 0.1at% and the like.

[0021] The present application designs gradient doping distribution of lanthanum and boron in the precursor inner core. The uniform distribution of boron from the inside to the outside of the entire inner core stage and the doping of lanthanum in the pure core can better improve the stability of the material bulk phase structure, effectively inhibit the lattice oxygen precipitation and the collapse of the layered structure in the high-voltage cycle process. At the same time, the doping mass of boron in the inner core is relatively higher, while the doping mass of boron in the core layer is relatively lower, which can better alleviate the Li + The increase of diffusion resistance ensures that the design of the core high-concentration transition layer can slow down the stress of large-particle positive electrode materials in the cycle process and avoid interface fracture.

[0022] Preferably, the chemical formula of the nickel-cobalt-manganese hydroxide precursor material is Ni x Co y Mn z (OH)2, x≥0.9, y>0, 0

[0023] For example, x can be 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98 or 0.99, etc., y can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08 or 0.09, etc., and z can be 0.01, 0.02, 0.03, 0.04 or 0.05, etc.

[0024] Preferably, in the direction from the inside to the outside, the mass fraction of nickel-cobalt-manganese oxide in the second coating layer gradually decreases, and the mass fraction of high-entropy oxide material gradually increases.

[0025] The second coating layer plays a transition role from the first coating layer to the third coating layer, that is, from pure nickel-cobalt-manganese oxide material to pure high-entropy oxide material. By gradually reducing the mass fraction of nickel-cobalt-manganese oxide in the second coating layer from the inside to the outside (that is, in the thickness direction from the first coating layer to the third coating layer), and gradually increasing the mass fraction of high-entropy oxide material from the inside to the outside, a smooth transition of mechanical and chemical properties is realized, the connection between layers is improved, and the coating layer is tightly coated to achieve better effect.

[0026] Preferably, the metal elements in the high-entropy oxide include Al, Ti, Zr, Hf and Ta.

[0027] Preferably, the Al, Ti, Zr, Hf and Ta are in equal molar ratio or near equal molar ratio, that is, the molar mass ratio is the same or nearly the same.

[0028] Preferably, in the positive electrode precursor material, the molar ratio of nickel, cobalt and manganese in the precursor inner core, the first coating layer and the second coating layer is consistent.

[0029] In a second aspect, the present application provides a preparation method of the positive electrode precursor material according to the first aspect, comprising the following steps:

[0030] (1) mixing a first nickel-cobalt-manganese mixed salt solution, a lanthanum source solution, a boron source solution, a precipitant solution and a complexing agent solution to perform a co-precipitation reaction to obtain a precursor inner core;

[0031] (2) performing a first coating treatment on the precursor inner core by using an electrospray deposition method with a second nickel-cobalt-manganese mixed salt solution to form a first coating layer, then performing a second coating treatment on the surface of the first coating layer by using the electrospray deposition method with the second nickel-cobalt-manganese mixed salt solution and a high-entropy mixed salt solution to form a second coating layer, and finally performing a coating treatment on the second coating layer by using the electrospray deposition method with the high-entropy mixed salt solution to obtain the positive electrode precursor material.

[0032] It should be noted that the electrospray deposition method in the present application is an electrostatic spraying method, that is, the material to be coated is uniformly dispersed on an electrostatic shielding rotary disc collector; then the coating agent solution is atomized into charged micron / nanometer droplets by a spraying channel; under the action of a high-voltage electrostatic field, these charged droplets are accelerated and uniformly sprayed and deposited onto the surface of the material to be coated below; the atomized aerosol can be transported to a heated reaction chamber by using a carrier gas (such as N2); the solvent evaporates rapidly in an instant when the droplets hit the high-temperature particle surface, the coating source simultaneously undergoes a thermal decomposition reaction, the corresponding metal oxide is generated and firmly adheres to the particle surface of the layer to be coated, and the electrospray deposition is completed.

[0033] The present application uses a co-precipitation method to make lanthanum and boron phase-doped in a nickel-cobalt-manganese hydroxide precursor material, thereby playing a synergistic effect of the two; and then the electrospray deposition method is used to realize the sequential coating treatment of the first coating layer, the second coating layer and the third coating layer, compared with the conventional solid-phase sintering coating method, the problem of uneven distribution of elements and component segregation after high-entropy element sintering coating is avoided; the effects of nickel-cobalt-manganese oxide material and high-entropy oxide material are effectively played; a product with stable structure and excellent coating effect is obtained; and the preparation process is simple and does not require a complex treatment process.

[0034] Preferably, the concentration of the first nickel-cobalt-manganese mixed salt solution is 1 mol / L to 3 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L, etc.

[0035] Preferably, the concentration of the boron source is 0.01-0.1 mol / L, for example 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1 mol / L, etc.

[0036] Preferably, the concentration of the lanthanum source is 0.01-0.05 mol / L, for example 0.01, 0.02, 0.03, 0.04 or 0.05 mol / L, etc.

[0037] Preferably, step (1) comprises:

[0038] The first nickel-cobalt-manganese mixed salt solution, the lanthanum source solution, the boron source solution, the precipitant solution and the complexing agent solution are mixed to perform a first co-precipitation reaction to obtain a core; then the core is used as a seed crystal, and the first nickel-cobalt-manganese mixed salt solution, the boron source solution, the precipitant solution and the complexing agent solution are mixed to perform a second co-precipitation reaction to obtain a precursor inner core.

[0039] Preferably, the reaction temperature of the first co-precipitation reaction and the second co-precipitation reaction is independently 30-80℃, for example 30, 40, 50, 60, 70 or 80℃, etc.

[0040] Preferably, the pH value of the first co-precipitation reaction is 11-11.5, for example 11, 11.1, 11.2, 11.3, 11.4 or 11.5, etc.

[0041] Preferably, the pH value of the second co-precipitation reaction is 10-10.5, for example 10, 10.2, 10.3, 10.4 or 10.5, etc.

[0042] Preferably, the median particle size D50 of the core is 2-3.5 μm, for example 2, 2.5, 3 or 3.5 μm, etc.

[0043] Preferably, the median particle size D50 of the precursor inner core is >8 μm, for example 8.5, 9, 9.5, 10, 10.5, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 μm, etc.

[0044] The present application obtains the precursor core doped with lanthanum and boron and the core layer doped with boron only through the segmented coprecipitation reaction in the coprecipitation reaction process, realizes the gradient distribution of boron from the core to the core layer by adjusting the raw material concentration, the feeding amount and the reaction condition in the preparation process, the high boron content in the core and the low boron content in the shell can stabilize the structure, relieve the increase of Li+ diffusion resistance caused by doping, slow down the stress of the large particle positive electrode material in the cycle process and avoid the interface fracture.

[0045] Preferably, the second nickel-cobalt-manganese mixed salt solution in step (2) comprises nickel-cobalt-manganese acetate and ethanol.

[0046] Preferably, the concentration of the second nickel-cobalt-manganese mixed salt solution in step (2) is 0.05 mol / L to 0.5 mol / L, for example, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.5 mol / L or 0.4 mol / L, etc.

[0047] Preferably, the concentration of the high-entropy mixed salt solution in step (2) is 0.05 mol / L to 0.5 mol / L, for example, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.5 mol / L or 0.4 mol / L, etc.

[0048] Preferably, in the first coating process in step (2), the flow rate of the second nickel-cobalt-manganese mixed salt solution is 0.5 mL / min to 1 mL / min, for example, 0.5 mL / min, 0.6 mL / min, 0.7 mL / min, 0.8 mL / min, 0.9 mL / min or 1 mL / min, etc.

[0049] Preferably, in the third coating process in step (2), the flow rate of the high-entropy mixed salt solution is 0.5 mL / min to 1 mL / min, for example, 0.5 mL / min, 0.6 mL / min, 0.7 mL / min, 0.8 mL / min, 0.9 mL / min or 1 mL / min, etc.

[0050] Preferably, the time of the first coating process in step (2) is 3 min to 10 min, for example, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, etc.

[0051] Preferably, the time of the second coating process in step (2) is 5 min to 15 min, for example, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min or 15 min, etc.

[0052] Preferably, the third coating treatment in step (2) is performed for 5-15 minutes, for example, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, or 15 minutes, etc.

[0053] The present application controls the time of each coating treatment stage, thereby achieving control of the coating thickness of the first coating layer, the second coating layer, and the third coating layer, better improving the stress matching and structural compactness between the multiple layers, ensuring efficient transmission of lithium ions in the high-entropy interface, and significantly enhancing the inhibition of electrolyte corrosion and oxygen precipitation of the entire material, ultimately achieving the synergistic optimization of high capacity, long cycle, and high safety.

[0054] Preferably, in the second coating treatment in step (2), the flow rate of the second nickel-cobalt-manganese mixed salt solution gradually decreases from the initial flow rate, and the flow rate of the high-entropy mixed salt solution gradually increases from the initial flow rate.

[0055] Notably, in the second coating treatment, the flow rates of the second nickel-cobalt-manganese mixed salt solution and the high-entropy mixed salt solution are linearly decreased and linearly increased, respectively, and the linear change trends are the same, which is more conducive to obtaining a second coating layer with a regular gradual change in content, thereby playing a transitional role in excellent mechanical and chemical properties.

[0056] Preferably, in the second coating treatment in step (2), the initial flow rate of the second nickel-cobalt-manganese mixed salt solution is 0.5-1 mL / min, for example, 0.5 mL / min, 0.6 mL / min, 0.7 mL / min, 0.8 mL / min, 0.9 mL / min, or 1 mL / min, etc., and the initial flow rate of the high-entropy mixed salt solution is 0 mL / min.

[0057] It can be understood that other features of the raw materials and more specific preparation details in the co-precipitation reaction stage are conventional technical solutions, and under the premise of not violating the technical concept of the present application, a person skilled in the art can adaptively select and adjust the conventional technical solutions according to actual needs.

[0058] Optionally, the types of salts in the nickel-cobalt-manganese mixed salt solution include, but are not limited to, at least one of chloride, sulfate, nitrate, or acetate, etc.

[0059] Optionally, the boron doping source includes, but is not limited to, metaborate, for example, sodium metaborate.

[0060] Optionally, the precipitant includes, but is not limited to, sodium hydroxide and / or potassium hydroxide.

[0061] Optionally, the mass concentration of the precipitant solution is 10% to 30%, for example, 10%, 15%, 20%, 25%, or 30%, etc.

[0062] Optionally, the complexing agent includes, but is not limited to, at least one of ammonia, citric acid, or ethylenediaminetetraacetic acid (EDTA), etc.

[0063] Optionally, the mass concentration of the complexing agent solution is 5% to 20%, for example, 5%, 10%, 15%, or 20%, etc.

[0064] Optionally, after the co-precipitation reaction is completely finished, the slurry after the reaction can be sequentially subjected to aging, washing, and drying treatments.

[0065] It should be further noted that the electrospray deposition in the present application can be realized by using an existing electrostatic spraying device with a double spraying pillow, i.e., a double-channel electrostatic spraying device, and other parameters in the preparation process can be adaptively selected and adjusted by the person skilled in the art according to actual needs.

[0066] Optionally, the voltage value of the electrospray deposition is 8 kV to 15 kV, for example, 8 kV, 9 kV, 10 kV, 11 kV, 12 kV, 13 kV, 14 kV, or 15 kV, etc.

[0067] Optionally, the vertical distance from the spraying needle to the collection device in the electrospray deposition is 4 cm to 8 cm, for example, 4 cm, 5 cm, 6 cm, 7 cm, or 8 cm, etc.

[0068] In a third aspect, the present application provides a positive electrode material, which is obtained by mixing and sintering the positive electrode precursor material prepared by the preparation method of the second aspect and a substance including at least a lithium source.

[0069] It can be understood that the present application does not specially limit the specific preparation method of the positive electrode material, and the method for obtaining the positive electrode material from the corresponding positive electrode precursor material within the reasonable range known by the person skilled in the art without violating the technical concept of the present application is applicable in principle.

[0070] Optionally, the lithium source includes, but is not limited to, at least one of lithium hydroxide, lithium carbonate, lithium nitrate, or lithium acetate, etc.

[0071] Optionally, the ratio of the total molar amount of nickel, cobalt, and manganese in the positive electrode precursor material to the molar amount of lithium in the lithium source is 1: (1 to 1.3), for example, 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.2, 1:1.25, or 1:3, etc., but is not limited to the listed values, and other unlisted values within the value range are also applicable.

[0072] Optionally, the sintering atmosphere is not unique, and those skilled in the art can adaptively select and adjust according to actual needs, for example, it can be a protective atmosphere or an oxygen-containing atmosphere, the protective atmosphere includes nitrogen and / or inert gas (argon or helium), and the oxygen-containing atmosphere includes air, oxygen or a mixed gas of oxygen and non-reactive gas.

[0073] Optionally, the sintering can be one-stage sintering or multi-stage sintering, and the specific sintering process can be adaptively selected and adjusted by those skilled in the art according to actual needs.

[0074] Optionally, the sintering temperature is 600-1000℃, for example, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃ or 1000℃, but is not limited to the listed values, and other unlisted values in this range are also applicable.

[0075] In a fourth aspect, the application further provides a lithium ion battery, which comprises the positive electrode material according to the third aspect.

[0076] Compared with the prior art, the application has the following beneficial effects:

[0077] (1) The positive electrode precursor material of the application has high tap density, low specific surface area and excellent volumetric energy density, adopts a unique core-shell structure design, and the precursor material core doped with lanthanum and boron occupies the Li site to inhibit phase change, and lanthanum strengthens the stability of the oxygen framework, thereby improving the bulk structure stability, reducing the stress of large particle positive electrode materials during the cycle process, and avoiding interface fracture; and then synergistically acting with the multi-stage coating layer structure, the first coating layer containing nickel-cobalt-manganese oxide can have good lattice matching and binding effect with the precursor core, the second coating layer of the mixed material of nickel-cobalt-manganese oxide and high-entropy oxide realizes smooth transition of mechanical and chemical properties from the precursor core to the high-entropy oxide layer, and then to the third coating layer only with high-entropy oxide, thereby improving the chemical and electrochemical inert protection, and utilizing the characteristics of high-entropy oxide, so that high-entropy elements diffuse from the inside to the surface layer, repair lattice defects, inhibit the occurrence of interface side reactions, and also improve the thermal stability of the material, inhibit H2-H3 phase change; at the same time, the coating layer structure can also relieve the mechanical stress caused by volume change and phase change in the core, prevent structure damage and performance degradation, and improve the capacity, rate and cycle performance of the positive electrode material.

[0078] (2) The present application adopts the co-precipitation method to make lanthanum and boron doped in the nickel-cobalt-manganese hydroxide precursor material, thereby playing the synergistic effect of both; and then the first coating layer, the second coating layer and the third coating layer are sequentially coated by the electrospray deposition method, compared with the conventional solid-phase sintering coating method, the uneven distribution of elements after high-entropy element sintering coating and the component segregation problem are avoided, the effect of the nickel-cobalt-manganese oxide material and the high-entropy oxide material is effectively played, the product with stable structure and excellent coating effect is obtained, and the preparation process is simple and does not need a complex treatment process. DETAILED DESCRIPTION

[0079] The technical solutions of the present application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present application and should not be regarded as specific limitations on the present application.

[0080] The "range" disclosed in the present application can be limited in the form of lower limit and upper limit, a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit limit the boundary of the specific range. The range limited in this way can include or not include the end value, either end value can be independently included or not included, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if the ranges of 60-120 and 80-110 are listed for a specific parameter, it is understood that the ranges of 60-110 and 80-120 are also expected. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4 and 5 are also listed, the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise stated, the numerical range "a-b" represents a shorthand representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is only a shorthand representation of these numerical combinations. In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to listing the parameter as, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when it is stated that a parameter is an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9 and 10.

[0081] In the present application, "combination of at least two" is referred to, without specific limitation, as greater than or equal to 2 in quantity. For example, "any one or a combination of at least two" means one or greater than or equal to two. It can be understood that when "combination of at least two" is referred to, it means a combination of any suitable number of items, that is, a combination of "at least two" items in a manner that is not conflicting and can implement the present application.

[0082] If not particularly specified, all the embodiments and optional embodiments of the present application can be combined to form new technical solutions.

[0083] The phrase "embodiment" mentioned in the present application means that the specific features, structures or properties described in connection with the embodiment can be included in at least one embodiment or embodiment of the present application. The appearance of this phrase in the specification does not necessarily mean the same embodiment, nor is it an independent or alternative embodiment to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in the present application can be combined with other embodiments.

[0084] Those skilled in the art can understand that in the method of each embodiment, the writing order of each step does not mean a strict execution order, and the detailed execution order of each step should be determined by its function and possible internal logic. If not particularly specified, all the steps of the present application can be performed in sequence, or randomly, and can be preferably performed in sequence. For example, the method comprises step (a) and step (b), which means that the method can comprise step (a) and step (b) performed in sequence, or step (b) and step (a) performed in sequence. For example, the method can also comprise step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0085] In the present application, the open technical features or technical solutions described by the words such as "include" do not exclude additional members other than the listed members, and can be regarded as providing both the closed features or technical solutions composed of the listed members and the open features or solutions including additional members in addition to the listed members. For example, A includes a1, a2 and a3, and unless otherwise specified, it can also include other members, or it can not include additional members, and it can be regarded as providing the technical features or technical solutions of "A consists of a1, a2 and a3" or "A is selected from a1, a2 and a3", and also providing the technical features or technical solutions of "A includes a1, a2 and a3, and also includes other members".

[0086] In the present application, if no other description is given, the "and / or" corresponding feature or scheme includes any one of two or more related listed items, and also includes any and all combinations of the related listed items, which includes any two related listed items, any more related listed items, or all related listed items. For example, "A and / or B" indicates a group consisting of A, B, and a combination of A and B. Wherein, "including A and / or B" can indicate "including A, including B, and including A and B", and can also indicate "including A, including B, or including A and B", which can be understood according to the sentence.

[0087] In the present application, the terms "first", "second", "third", "fourth" and the like in "first aspect", "second aspect", "third aspect", "fourth aspect" and the like are only for description purpose, and cannot be understood as indicating or implying relative importance or quantity, and also cannot be understood as implying the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth" and the like only play a non-exhaustive enumeration description purpose, and it should be understood that they do not constitute a closed limitation on the quantity.

[0088] In the present application, "optional" means optional, that is, selected from any one of the two parallel schemes of "yes" or "no". If there are multiple "optional" in a technical scheme, if no special description is given, and there is no contradiction or mutual restriction relationship, each "optional" is independent.

[0089] In the present application, "room temperature" generally refers to 4℃~35℃, and can refer to 20℃±5℃. In some embodiments of the present application, room temperature refers to 20℃~30℃.

[0090] Embodiment 1

[0091] The positive electrode precursor material provided in the embodiment comprises, from inside to outside, a precursor inner core, a first coating layer, a second coating layer and a third coating layer.

[0092] The precursor inner core comprises a core and a core layer coated on the surface of the core, and the first coating layer is coated on the surface of the core layer.

[0093] The core comprises a nickel-cobalt-manganese hydroxide precursor material Ni 0.93 Co 0.04 Mn 0.03 (OH)2 and lanthanum and boron doped in the nickel-cobalt-manganese hydroxide precursor material (the doping amount of lanthanum is 0.1at%, and the doping amount of boron is 0.05at%);

[0094] The core layer comprises a nickel-cobalt-manganese hydroxide precursor material Ni 0.93 Co0.04 Mn 0.03 (OH)2and boron doped in the nickel-cobalt-manganese hydroxide precursor material (the doping amount of boron is 0.05 at%);

[0095] The first coating layer comprises nickel-cobalt-manganese oxide Ni 0.93 Co 0.04 Mn 0.03 O2, the second coating layer comprises nickel-cobalt-manganese oxide Ni 0.93 Co 0.04 Mn 0.03 O2and high-entropy oxide (AlTiZrHfTa)O2, and the third coating layer comprises high-entropy oxide (AlTiZrHfTa)O2;

[0096] In the direction from inside to outside, the mass fraction of nickel-cobalt-manganese oxide in the second coating layer gradually decreases, and the mass fraction of high-entropy oxide material gradually increases.

[0097] The preparation method of the positive electrode precursor material is as follows:

[0098] (1) A nickel-cobalt-manganese mixed sulfate solution with a molar ratio of nickel, cobalt and manganese of 93:4:3 is prepared, and the total concentration of metal ions is 1.5 mol / L, a lanthanum sulfate solution with a concentration of 0.05 mol / L is prepared, a boric acid solution with a concentration of 0.02 mol / L is prepared, a sodium hydroxide solution with a mass concentration of 22% is prepared as a precipitant solution, and an ammonia solution with a mass concentration of 18% is prepared as a complexing agent solution;

[0099] (2) Water is injected into the reaction kettle to half the volume of the reaction kettle, the stirring speed is set to 400 rpm, the temperature is controlled at 50℃, and then the ammonia and sodium hydroxide are added to prepare the bottom liquid, and the pH of the bottom liquid is 11;

[0100] The nickel-cobalt-manganese mixed sulfate solution, the lanthanum sulfate solution, the boric acid solution, the precipitant solution and the complexing agent solution are added to the bottom liquid in parallel flow to carry out the first co-precipitation reaction, the reaction temperature is 40℃, the pH value during the reaction is 11.5, and the rotation speed is 380 rpm, and a crystal seed (i.e. a core) with a median particle size D50 of 3μm is obtained;

[0101] Then the obtained crystal seed is re-injected into the bottom liquid, the feeding of the lanthanum sulfate is stopped, and the nickel-cobalt-manganese mixed sulfate solution, the lanthanum sulfate solution, the boric acid solution, the precipitant solution and the complexing agent solution are continuously added to the reaction liquid containing the crystal seed in parallel flow to carry out the second co-precipitation reaction, the reaction temperature is 40℃, the pH value during the reaction is 10.5, and the rotation speed is 380 rpm, and a precursor inner core (i.e. a core and a nuclear layer coated on the surface of the core) with a median particle size D50 of 10μm is obtained, the reaction is stopped, and aging, washing and drying are continuously carried out to obtain a finished product precursor inner core;

[0102] (3) uniformly dispersing the precursor inner core on the electrostatic shielding rotary disc collector, and performing coating treatment by using an electrospray deposition method, wherein the voltage value of the high-voltage electrostatic field is 10 kV, and the coating treatment specifically comprises:

[0103] Then, an ethanol solution of nickel-cobalt-manganese (molar ratio of nickel, cobalt and manganese is 93:4:3) sulfate with a concentration of 0.1 mol / L is atomized to form charged droplets under the action of the high-voltage electrostatic field by using the spraying channel (spraying needle) A, and the flow rate is 0.8 mL / min. The first coating treatment is performed on the precursor inner core for 5 min to form a first coating layer.

[0104] Then, the ethanol solution of nickel-cobalt-manganese sulfate is treated by using the spraying channel A, and the ethanol solution of AlTiZrHfTa (equal molar ratio of each element) mixed sulfate with a concentration of 0.1 mol / L is treated by using the spraying channel B. The second coating treatment is simultaneously performed on the spraying channel A and the spraying channel B for 10 min, wherein the initial flow rate of the spraying channel A is 0.8 mL / min, and the initial flow rate of the spraying channel B is 0 mL / min. During the second coating treatment, the flow rate of the spraying channel A gradually decreases, and the flow rate of the spraying channel B gradually increases, so as to form a second coating layer coated on the surface of the first coating layer.

[0105] Finally, the ethanol solution of AlTiZrHfTa (equal molar ratio of each element) mixed sulfate with a concentration of 0.1 mol / L is treated by using the spraying channel B, and the flow rate is 0.8 mL / min. The third coating treatment is performed for 5 min to form a third coating layer coated on the surface of the second coating layer, so as to obtain the positive electrode precursor material.

[0106] Embodiment 2

[0107] The embodiment is different from embodiment 1 in that the embodiment provides a positive electrode precursor material, and the positive electrode precursor material sequentially comprises a precursor inner core, a first coating layer, a second coating layer and a third coating layer from inside to outside.

[0108] The precursor inner core comprises a core and a core layer coated on the surface of the core, and the first coating layer is coated on the surface of the core layer.

[0109] The core comprises a nickel-cobalt-manganese hydroxide precursor material Ni 0.93 Co 0.04 Mn 0.03 (OH)2 and lanthanum and boron elements doped in the nickel-cobalt-manganese hydroxide precursor material (doping amount of lanthanum is 0.08 at%, and doping amount of boron is 0.08 at%);

[0110] The core layer comprises a nickel-cobalt-manganese hydroxide precursor material Ni 0.93 Co0.04 Mn 0.03 (OH)2and boron doped in the nickel-cobalt-manganese hydroxide precursor material (the doping amount of boron is 0.08 at%);

[0111] The first coating layer comprises nickel-cobalt-manganese oxide Ni 0.93 Co 0.04 Mn 0.03 O2, the second coating layer comprises nickel-cobalt-manganese oxide Ni 0.93 Co 0.04 Mn 0.03 O2and high-entropy oxide (AlTiZrHfTa)O2, and the third coating layer comprises high-entropy oxide (AlTiZrHfTa)O2;

[0112] In the direction from inside to outside, the mass fraction of nickel-cobalt-manganese oxide in the second coating layer gradually decreases, and the mass fraction of high-entropy oxide material gradually increases.

[0113] The preparation method of the positive electrode precursor material is as follows:

[0114] (1) A nickel-cobalt-manganese mixed sulfate solution with a molar ratio of nickel, cobalt and manganese of 93:4:3 is prepared, and the total concentration of metal ions is 1.5 mol / L, a lanthanum sulfate solution with a concentration of 0.05 mol / L is prepared, a boric acid solution with a concentration of 0.02 mol / L is prepared, a sodium hydroxide solution with a mass concentration of 22% is prepared as a precipitant solution, and an ammonia solution with a mass concentration of 18% is prepared as a complexing agent solution;

[0115] (2) Water is injected into the reaction kettle to half the volume of the reaction kettle, the stirring speed is set to 400 rpm, the temperature is controlled at 50℃, and then the ammonia and sodium hydroxide are added to prepare the bottom liquid, and the pH of the bottom liquid is 11;

[0116] The nickel-cobalt-manganese mixed sulfate solution, the lanthanum sulfate solution, the boric acid solution, the precipitant solution and the complexing agent solution are added to the bottom liquid in parallel flow to carry out the first co-precipitation reaction, the reaction temperature is 60℃, the pH value during the reaction is 11, the rotation speed is 400 rpm, and the crystal seed (i.e. the core) with a median particle size D50 of 3.5 μm is obtained;

[0117] Then the obtained crystal seed is re-injected into the bottom liquid, the feeding of the lanthanum sulfate is stopped, and the nickel-cobalt-manganese mixed sulfate solution, the lanthanum sulfate solution, the boric acid solution, the precipitant solution and the complexing agent solution are continuously added to the reaction liquid containing the crystal seed in parallel flow to carry out the second co-precipitation reaction, the reaction temperature is 60℃, the pH value during the reaction is 10, the rotation speed is 400 rpm, and the precursor inner core (i.e. the core and the nuclear layer coated on the surface of the core) with a median particle size D50 of 12 μm is obtained, the reaction is stopped, and aging, washing and drying are continuously carried out to obtain the finished product precursor inner core.

[0118] (3) uniformly dispersing the precursor inner core on the electrostatic shielding rotary disc collector, and performing coating treatment by using an electrospray deposition method, wherein the voltage value of the high-voltage electrostatic field is 8 kV, and the coating treatment specifically comprises:

[0119] Then, an ethanol solution of nickel-cobalt-manganese (molar ratio of nickel, cobalt and manganese is 93:4:3) sulfate with a concentration of 0.5 mol / L is atomized to form charged droplets under the action of the high-voltage electrostatic field by using the spraying channel (spraying needle) A, and the flow rate is 1 mL / min. The first coating treatment is performed on the precursor inner core for 3 min to form a first coating layer.

[0120] Then, the ethanol solution of nickel-cobalt-manganese sulfate is treated by using the spraying channel A, and the ethanol solution of AlTiZrHfTa (equal molar ratio of each element) mixed sulfate with a concentration of 0.5 mol / L is treated by using the spraying channel B. The second coating treatment is simultaneously performed on the spraying channel A and the spraying channel B for 5 min, wherein the initial flow rate of the spraying channel A is 1 mL / min, and the initial flow rate of the spraying channel B is 0 mL / min. During the second coating treatment, the flow rate of the spraying channel A gradually decreases, and the flow rate of the spraying channel B gradually increases to form a second coating layer coated on the surface of the first coating layer.

[0121] Finally, the ethanol solution of AlTiZrHfTa (equal molar ratio of each element) mixed sulfate with a concentration of 0.1 mol / L is treated by using the spraying channel B, and the flow rate is 1 mL / min. The third coating treatment is performed for 3 min to form a third coating layer coated on the surface of the second coating layer, thereby obtaining the positive electrode precursor material.

[0122] Example 3

[0123] The positive electrode precursor material comprises a precursor inner core, a first coating layer, a second coating layer and a third coating layer from inside to outside.

[0124] The precursor inner core comprises a core and a core layer coated on the surface of the core, and the first coating layer is coated on the surface of the core layer.

[0125] The core comprises a nickel-cobalt-manganese hydroxide precursor material Ni 0.93 Co 0.04 Mn 0.03 (OH)2 and lanthanum and boron elements doped in the nickel-cobalt-manganese hydroxide precursor material (doping amount of lanthanum is 0.12 at%, and doping amount of boron is 0.03 at%);

[0126] The core layer comprises a nickel-cobalt-manganese hydroxide precursor material Ni 0.93 Co 0.04 Mn0.03 (OH)2 and boron doped in the nickel-cobalt-manganese hydroxide precursor material (the doping amount of boron is 0.03 at%);

[0127] The first coating layer comprises nickel-cobalt-manganese oxide Ni 0.93 Co 0.04 Mn 0.03 O2, the second coating layer comprises nickel-cobalt-manganese oxide Ni 0.93 Co 0.04 Mn 0.03 O2 and a mixed material of high-entropy oxide (AlTiZrHfTa)O2, and the third coating layer comprises high-entropy oxide (AlTiZrHfTa)O2;

[0128] In the direction from inside to outside, the mass fraction of nickel-cobalt-manganese oxide in the second coating layer gradually decreases, and the mass fraction of high-entropy oxide material gradually increases.

[0129] The preparation method of the positive electrode precursor material is as follows:

[0130] (1) A nickel-cobalt-manganese mixed sulfate solution with a molar ratio of nickel, cobalt and manganese of 93:4:3 is prepared, and the total concentration of metal ions is 3 mol / L, a lanthanum sulfate solution with a concentration of 0.1 mol / L is prepared, a boric acid solution with a concentration of 0.05 mol / L is prepared, a sodium hydroxide solution with a mass concentration of 15% is prepared as a precipitant solution, and an ammonia solution with a mass concentration of 10 is prepared as a complexing agent solution;

[0131] (2) Water is injected into the reaction kettle to half the volume of the reaction kettle, the stirring speed is set to 400 rpm, the temperature is controlled at 45℃, and then the ammonia water and sodium hydroxide are added to prepare the bottom liquid, and the pH of the bottom liquid is 11.3;

[0132] The nickel-cobalt-manganese mixed sulfate solution, the lanthanum sulfate solution, the boric acid solution, the precipitant solution and the complexing agent solution are added to the bottom liquid in parallel flow to carry out the first co-precipitation reaction, the reaction temperature is 40℃, the pH value during the reaction is 11.5, and the rotation speed is 380 rpm, and a crystal seed (i.e. a core) with a median particle size D50 of 2 μm is obtained;

[0133] Then the obtained crystal seed is re-injected into the bottom liquid, the feeding of the lanthanum sulfate is stopped, and the nickel-cobalt-manganese mixed sulfate solution, the lanthanum sulfate solution, the boric acid solution, the precipitant solution and the complexing agent solution are continuously added to the reaction liquid containing the crystal seed in parallel flow to carry out the second co-precipitation reaction, the reaction temperature is 40℃, the pH value during the reaction is 11.5, and the rotation speed is 380 rpm, and a precursor inner core (i.e. a core and a nuclear layer coated on the surface of the core) with a median particle size D50 of 8.5 μm is obtained, the reaction is stopped, and aging, washing and drying are continuously carried out to obtain a finished product precursor inner core;

[0134] (3) uniformly dispersing the precursor core on the electrostatic shielding rotary disc collector, and performing coating treatment by using an electrospray deposition method, wherein the voltage value of the high-voltage electrostatic field is 15 kV, and the coating treatment specifically comprises the following steps:

[0135] Then, the ethanol solution of nickel-cobalt-manganese (molar ratio of nickel, cobalt and manganese is 93:4:3) sulfate with a concentration of 0.05 mol / L is atomized to form charged droplets under the action of the high-voltage electrostatic field by using the spray channel (spray needle) A, and the flow rate is 0.5 mL / min. The first coating treatment is performed on the precursor core for 10 min to form a first coating layer.

[0136] Then, the ethanol solution of nickel-cobalt-manganese sulfate is treated by using the spray channel A, and the ethanol solution of AlTiZrHfTa (equal molar ratio of each element) mixed sulfate with a concentration of 0.051 mol / L is treated by using the spray channel B. The second coating treatment is simultaneously performed on the spray channel A and the spray channel B for 15 min, wherein the initial flow rate of the spray channel A is 0.8 mL / min, and the initial flow rate of the spray channel B is 0 mL / min. During the second coating treatment, the flow rate of the spray channel A gradually decreases, and the flow rate of the spray channel B gradually increases, so as to form a second coating layer coated on the surface of the first coating layer.

[0137] Finally, the ethanol solution of AlTiZrHfTa (equal molar ratio of each element) mixed sulfate with a concentration of 0.05 mol / L is treated by using the spray channel B, and the flow rate is 0.5 mL / min. The third coating treatment is performed for 10 min to form a third coating layer coated on the surface of the second coating layer, so as to obtain the positive electrode precursor material.

[0138] Example 4

[0139] The difference between the present example and Example 1 is that the molar ratio of nickel, cobalt and manganese in the present example is 91:6:3.

[0140] In the preparation method, the molar ratio of nickel, cobalt and manganese in all the corresponding nickel-cobalt-manganese mixed salts is adaptively adjusted.

[0141] The remaining conditions are consistent with those in Example 1.

[0142] Example 5

[0143] The difference between the present example and Example 1 is that the positive electrode precursor core in the present example is simultaneously doped with lanthanum and boron from inside to outside, i.e., without the distinction between the core and the core layer.

[0144] In step (2) of the preparation method, the first coprecipitation reaction is performed until the precursor core with a median particle size D50 of 10 μm is obtained.

[0145] The remaining conditions are consistent with those in Example 1.

[0146] Example 6

[0147] The difference between this example and Example 1 is that only boron is doped in the core of this example, and lanthanum and boron are doped in the core layer.

[0148] In step (2) of the preparation method, the feeding materials of the first co-precipitation reaction and the second co-precipitation reaction are exchanged.

[0149] The remaining conditions are consistent with those of Example 1.

[0150] Example 7

[0151] The difference between this example and Example 1 is that only lanthanum is doped in the core layer of this example.

[0152] In step (2) of the preparation method, the boric acid solution is replaced by a lanthanum sulfate solution.

[0153] The remaining conditions are consistent with those of Example 1.

[0154] Example 8

[0155] The difference between this example and Example 1 is that the second coating layer of this example is a mixed material of nickel-cobalt-manganese oxide Ni 0.93 Co 0.04 Mn 0.03 O2 and high-entropy oxide (AlTiZrHfTa) O2, and is a uniform mixed material.

[0156] In the second coating treatment process of step (3) of the preparation method, the flow rates of spray channel A and spray channel B are both 0.4 mL / min, and throughout the coating treatment process, the flow rates are fixed and not increased or decreased.

[0157] The remaining conditions are consistent with those of Example 1.

[0158] Example 9

[0159] The difference between this example and Example 1 is that the first coating treatment time in step (3) of this example is 1 min.

[0160] The remaining conditions are consistent with those of Example 1.

[0161] Example 10

[0162] The difference between this example and Example 1 is that the first coating treatment time in step (3) of this example is 15 min.

[0163] The remaining conditions are consistent with those of Example 1.

[0164] Example 11

[0165] The difference between this example and Example 1 is that the time for the second coating treatment in step (3) of this example is 3 min.

[0166] The remaining conditions are consistent with Example 1.

[0167] Example 12

[0168] The difference between this example and Example 1 is that the time for the second coating treatment in step (3) of this example is 20 min.

[0169] The remaining conditions are consistent with Example 1.

[0170] Example 13

[0171] The difference between this example and Example 1 is that the time for the third coating treatment in step (3) of this example is 3 min.

[0172] The remaining conditions are consistent with Example 1.

[0173] Example 14

[0174] The difference between this example and Example 1 is that the time for the third coating treatment in step (3) of this example is 20 min.

[0175] The remaining conditions are consistent with Example 1.

[0176] Comparative Example 1

[0177] The difference between this comparative example and Example 1 is that the precursor core in this comparative example is not doped with lanthanum and boron elements.

[0178] In step (1) of the preparation method, the lanthanum source solution and the boron source solution are not prepared, and in step (2), the precursor core with a median particle size D50 of 10 μm is directly obtained by the first coprecipitation reaction.

[0179] The remaining conditions are consistent with Example 1.

[0180] Comparative Example 2

[0181] The difference between this comparative example and Example 1 is that the positive electrode precursor material in this comparative example does not contain a first coating layer, a second coating layer, and a third coating layer.

[0182] In the preparation method, step (3) is not performed.

[0183] The remaining conditions are consistent with Example 1.

[0184] Comparative Example 3

[0185] The difference between the present comparative example and Example 1 is that the positive electrode precursor material of the present comparative example does not contain the first coating layer.

[0186] In step (3) of the preparation method, the first coating treatment is not performed.

[0187] The remaining conditions are consistent with those of Example 1.

[0188] Comparative Example 4

[0189] The difference between the present comparative example and Example 1 is that the positive electrode precursor material of the present comparative example does not contain the second coating layer.

[0190] In step (3) of the preparation method, the second coating treatment is not performed.

[0191] The remaining conditions are consistent with those of Example 1.

[0192] Comparative Example 5

[0193] The difference between the present comparative example and Example 1 is that the positive electrode precursor material of the present comparative example does not contain the third coating layer.

[0194] In step (3) of the preparation method, the third coating treatment is not performed.

[0195] The remaining conditions are consistent with those of Example 1.

[0196] Battery preparation and performance test

[0197] (1) Battery preparation

[0198] The positive electrode precursor materials of the examples and comparative examples and lithium hydroxide were mixed uniformly at a molar ratio of 1:1.05, sintered at 750°C for 10h in an oxygen atmosphere, and then taken out, ground and crushed to obtain ternary positive electrode materials;

[0199] The positive electrode slurry was prepared according to the ratio of positive electrode material: SP: PVDF = 90:5:5, and the positive electrode slurry was obtained for standby, wherein the solid content of the slurry was 60%; the aluminum foil was placed on the coating machine, and the 150μm film applicator was placed on the aluminum foil, the single crystal slurry was poured in, and the equipment was started for coating. After coating, the pole piece was obtained, and the pole piece was placed in a 110°C oven for drying and rolling to obtain the positive electrode pole piece;

[0200] The positive electrode pole pieces provided by the examples and comparative examples were cut into 15mm diameter discs using a punch press in a dry environment, and a lithium metal sheet was used as the counter electrode in a glove box, a ceglard composite membrane was selected as the separator membrane, and a lithium ion battery was assembled by adding electrolyte. 1mol / L LiPF6 and EC:DEC:DMC=1:1:1(v / v) were used as the electrolyte (wherein, EC is ethylene carbonate; DEC is diethyl carbonate; and DMC is dimethyl carbonate).

[0201] (2) Performance test

[0202] The performance of the batteries provided in the examples and the comparative examples was tested by using Wuhan Lan Electric CT2001A system, and the test temperature was 25℃.

[0203] First discharge capacity test: the first charge-discharge test was performed at 0.1C rate in the voltage range of 2.8V-4.3V, and the first discharge capacity was obtained.

[0204] Cycle performance test: the charge-discharge cycle test was performed at 1C rate in the voltage range of 2.8V-4.3V, and the capacity retention rate after 300 cycles was obtained.

[0205] Rate performance test: the battery was charged at 1C rate in the voltage range of 2.8V-4.3V, and then discharged at 0.2C rate, and the discharge capacity C0.2C was obtained. 0.2 The battery was charged at 1C rate, and then discharged at 5C rate, and the discharge capacity C5 was obtained. 0.2 C5 / C0.2C is the rate performance.

[0206] Voltage attenuation test: the test was performed according to the test method of GB / T 31486-2015.

[0207] The test results of the above tests are shown in Table 1.

[0208] Table 1

[0209]

[0210] From Table 1, it can be concluded that:

[0211] The positive electrode precursor material and the preparation method provided by the application adopt a unique core-shell structure design, and the precursor material core doped with lanthanum and boron cooperates with the multi-level coating layer structure and the material of the coating layer, thereby improving the capacity, rate and cycle performance of the positive electrode material.

[0212] The data results of Example 1, Example 5, Example 6 and Example 7 show that the distribution of boron and lanthanum doping in the core plays an important role in the structural stability of the positive electrode precursor material, and through the uniform distribution of boron from the inside to the entire core stage and the doping of lanthanum in the pure core, the capacity, rate and cycle performance of the positive electrode material are further improved.

[0213] The data results of example 1, examples 7-14 show that in the coating process of the multi-stage coating layer, by controlling the coating time of each stage coating process and setting the gradual transition layer in the corresponding multi-stage coating layer, the effective control of the coating thickness of the multi-stage coating layer and the double stable transition of the coating layer components and mechanical properties are realized, the coating is more dense, the connection effect between the coating layers is stronger, so that the capacity, rate and cycle performance of the positive electrode material are improved.

[0214] The data results of example 1, examples 7-14 show that in the coating process of the multi-stage coating layer, by controlling the coating time of each stage coating process and setting the gradual transition layer in the corresponding multi-stage coating layer, the effective control of the coating thickness of the multi-stage coating layer and the double stable transition of the coating layer components and mechanical properties are realized, the coating is more dense, the connection effect between the coating layers is stronger, so that the capacity, rate and cycle performance of the positive electrode material are improved.

[0215] The applicant declares that the above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by any person skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A positive electrode precursor material, characterized in that, The positive electrode precursor material comprises, from the inside out, a precursor core, a first coating layer, a second coating layer, and a third coating layer; The precursor core includes a nickel cobalt manganese hydroxide precursor material and lanthanum and boron elements doped into the nickel cobalt manganese hydroxide precursor material. The first coating layer comprises nickel cobalt manganese oxide, the second coating layer comprises a mixture of nickel cobalt manganese oxide and high entropy oxide, and the third coating layer comprises high entropy oxide.

2. The positive electrode precursor material according to claim 1, characterized in that, The precursor core includes a core and a core layer covering the surface of the core, wherein the first covering layer covers the surface of the core layer; Preferably, the core comprises a nickel-cobalt-manganese hydroxide precursor material and lanthanum and boron elements doped into the nickel-cobalt-manganese hydroxide precursor material; Preferably, the doping amount of lanthanum in the core is 0.05 at% to 0.15 at%, and the doping amount of boron in the core is 0.01 at% to 0.1 at%. Preferably, the core layer comprises a nickel cobalt manganese hydroxide precursor material and boron doped in the nickel cobalt manganese hydroxide precursor material; Preferably, the boron doping amount in the core layer is 0.01 at% to 0.1 at%; Preferably, the general chemical formula of the nickel-cobalt-manganese hydroxide precursor material is Ni x Co y Mn z (OH)2, x≥0.9, y>0, 0<z≤0.05, and x+y+z=1.

3. The positive electrode precursor material according to claim 1 or 2, characterized in that, From the inside out, the mass percentage of nickel-cobalt-manganese oxides in the second coating layer gradually decreases, while the mass percentage of high-entropy oxide materials gradually increases. Preferably, the metal elements in the high-entropy oxide include Al, Ti, Zr, Hf, and Ta.

4. A method for preparing a positive electrode precursor material as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: (1) A co-precipitation reaction was carried out by mixing a first nickel-cobalt-manganese mixed salt solution, a lanthanum source solution, a boron source solution, a precipitant solution, and a complexing agent solution to obtain the precursor core; (2) The precursor core is coated with the second nickel-cobalt-manganese mixed salt solution by electrospray deposition to form a first coating layer. Then, the second nickel-cobalt-manganese mixed salt solution and the high-entropy mixed salt solution are coated with the first coating layer by electrospray deposition to form a second coating layer. Finally, the high-entropy mixed salt solution is coated with the second coating layer by electrospray deposition to obtain the cathode precursor material.

5. The preparation method according to claim 4, characterized in that, The concentration of the first nickel-cobalt-manganese mixed salt solution is 1 mol / L to 3 mol / L; Preferably, the concentration of the boron source is 0.01 mol / L to 0.1 mol / L; Preferably, the concentration of the lanthanum source is 0.01 mol / L to 0.05 mol / L; Preferably, step (1) includes: A first coprecipitation reaction is carried out by mixing a first nickel-cobalt-manganese mixed salt solution, a lanthanum source solution, a boron source solution, a precipitant solution, and a complexing agent solution to obtain a core. Then, using the core as a seed crystal, a second coprecipitation reaction is carried out by mixing the first nickel-cobalt-manganese mixed salt solution, a boron source solution, a precipitant solution, and a complexing agent solution to obtain a precursor core.

6. The preparation method according to claim 5, characterized in that, The reaction temperatures of the first coprecipitation reaction and the second coprecipitation reaction are each independently 30℃~80℃; Preferably, the pH value of the first coprecipitation reaction is 11~11.5; Preferably, the pH value of the second coprecipitation reaction is 10~10.5; Preferably, the median particle size D50 of the core is 2μm~3.5μm; Preferably, the median particle size D50 of the precursor kernel is greater than 8 μm.

7. The preparation method according to claim 4, characterized in that, Step (2) The second nickel-cobalt-manganese mixed salt solution comprises nickel-cobalt-manganese acetate and ethanol; Preferably, in step (2), the concentration of the second nickel-cobalt-manganese mixed salt solution is 0.05 mol / L to 0.5 mol / L; Preferably, the concentration of the high-entropy mixed salt solution in step (2) is 0.05 mol / L to 0.5 mol / L; Preferably, in step (2), during the first coating process, the flow rate of the second nickel-cobalt-manganese mixed salt solution is 0.5 mL / min to 1 mL / min; Preferably, in the third coating process described in step (2), the flow rate of the high-entropy mixed salt solution is 0.5 mL / min to 1 mL / min; Preferably, the time for the first coating treatment in step (2) is 3 min to 10 min; Preferably, the time for the second coating treatment in step (2) is 5 min to 15 min; Preferably, the time for the third coating process in step (2) is 5 min to 15 min.

8. The preparation method according to claim 4 or 7, characterized in that, In step (2), during the second coating process, the flow rate of the second nickel-cobalt-manganese mixed salt solution gradually decreases from the initial flow rate, while the flow rate of the high-entropy mixed salt solution gradually increases from the initial flow rate. Preferably, in step (2), during the second coating process, the initial flow rate of the second nickel-cobalt-manganese mixed salt solution is 0.5 mL / min to 1 mL / min, and the initial flow rate of the high-entropy mixed salt solution is 0 mL / min.

9. A positive electrode material, characterized in that, The cathode material is obtained by mixing and sintering a cathode precursor material as described in any one of claims 1-3 or a cathode precursor material prepared by the preparation method as described in any one of claims 4-8 with a substance comprising at least a lithium source.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode material as described in claim 9.

Images